Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands		3 Months Ended			9 Months Ended
		Oct. 31, 2018	Oct. 31, 2017	[1]	Oct. 31, 2018	Oct. 31, 2017
Cash flows from operating activities
Net income		$ 64,085	$ 34,925		$ 158,681	$ 110,523	[1]
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization		3,383	3,601		10,477	10,621	[1]
Amortization of premiums (accretion of discount) on short-term investments		(848)	365		(1,380)	1,207	[1]
Stock-based compensation		19,918	14,018		56,647	39,186	[1]
Amortization of deferred costs		4,595	4,203		13,697	12,338	[1]
Deferred income taxes		1,824	(44)		2,642	(987)	[1]
(Gain) Loss on foreign currency from market-to-market derivative		(19)	(134)		(182)	119	[1]
Bad debt expense (recovery)		84	(63)		262	(269)	[1]
Changes in operating assets and liabilities:
Accounts receivable		21,658	23,323		134,353	110,472	[1]
Unbilled accounts receivable		(5,212)	(4,852)		(6,641)	(5,331)	[1]
Deferred costs		(4,504)	(4,170)		(11,426)	(11,933)	[1]
Income taxes		1,029	6,125		525	4,063	[1]
Prepaid expenses and other current and long-term assets		(6,018)	(390)		(9,527)	(1,550)	[1]
Accounts payable		2,982	1,473		3,520	1,717	[1]
Accrued expenses and other current liabilities		406	1,405		(3,698)	1,949	[1]
Deferred revenue		(62,860)	(47,735)		(70,616)	(42,574)	[1]
Other long-term liabilities		1,053	184		1,620	2,450	[1]
Net cash provided by operating activities		41,556	32,234		278,954	232,001	[1]
Cash flows from investing activities
Purchases of short-term investments		(214,839)	(207,268)		(589,070)	(350,719)	[1]
Maturities and sales of short-term investments		130,137	74,806		447,947	203,183	[1]
Purchases of property and equipment		(4,163)	(1,635)		(5,558)	(8,130)	[1]
Capitalized internal-use software development costs		(495)	(301)		(1,009)	(1,334)	[1]
Net cash used in investing activities		(89,360)	(134,398)		(147,690)	(157,000)	[1]
Cash flows from financing activities
Proceeds from exercise of common stock options		4,867	3,747		19,728	17,163	[1]
Net cash provided by financing activities		4,867	3,747		19,728	17,163	[1]
Effect of exchange rate changes on cash, cash equivalents, and restricted cash		(1,154)	(12)		(3,530)	1,228	[1]
Net change in cash, cash equivalents, and restricted cash		(44,091)	(98,429)		147,462	93,392	[1]
Cash, cash equivalents, and restricted cash at beginning of period		512,940	410,428		321,387	218,607	[1]
Cash, cash equivalents, and restricted cash at end of period		468,849	311,999		468,849	311,999	[1]
Cash, cash equivalents, and restricted cash at end of period:
Cash and cash equivalents		467,643	310,796		467,643	310,796	[1]
Restricted cash included in other long-term assets		1,206	1,203		1,206	1,203	[1]
Cash, cash equivalents, and restricted cash at end of period		468,849	311,999		468,849	311,999	[1]
Supplemental disclosures of other cash flow information:
Cash paid for income taxes, net of refunds		6,697	2,106		17,268	8,142	[1]
Excess tax benefits from employee stock plans		12,006	8,654		31,032	37,329	[1]
Non-cash investing and financing activities:
Changes in accounts payable and accrued expenses related to property and equipment purchases		$ 314	$ (978)		$ 493	(1,099)	[1]
Vesting of early exercised stock options	[1]					$ 1

[1] See note 1 of the notes to the condensed consolidated financial statements for a summary of adjustments.